JP2000292386A - Pulse heat transfer test device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute safely a test for grasping precisely heat transfer characteristics of an instrument resisting a pulsating high heat flux. SOLUTION: This device is so composed that a current is carried to a heating element 3, and that a heating transfer surface 4 is overheated by an electric power, and that heat transfer characteristic from the heating surface 4 is tested. In this case, an electric power for heating is accumulated in an accumulating device 10, and accumulated electric energy is sent instantly to the heating element 3, and pulsating heating transfer characteristics are grasped. And, this device has a charge/discharge device for charging the accumulating device 10 every time before one test, and for allowing the device 10 to discharge every time after finish of the test.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for testing a heat transfer characteristic from a heating element to a surrounding substance, which has a large heat flux in a pulsed manner, and more particularly to a cooling apparatus such as water from the heating element. The present invention relates to a test device for ascertaining the characteristics of transient heat transfer to a device.

[0002]

2. Description of the Related Art Heat transfer by boiling is used in many devices, but in many cases, steady heat transfer characteristics become a problem. Accordingly, conventionally, the heat transfer characteristics have been grasped by steadily generating heat from the heating element and constantly applying a heat flux. The apparatus is designed based on the heat transfer characteristics obtained in such a test, and a normal apparatus is operated stably.

FIG. 2 is a block diagram of a conventional heat transfer test apparatus. The commercial power is received, converted into a required voltage by a power receiving facility 1 such as a transformer, and then passed through a power control device 2 to supply necessary power to the heating element 3. The heat is transmitted to the heat transfer surface 4 and is released from the heat transfer surface to a coolant 5 such as water. Depending on the heat flux from the surface at this time, the characteristic of boiling heat transfer is
It changes with nucleate boiling and film boiling. The heat flux at the time of the change from nucleate boiling to film boiling is the maximum heat flux that can be usually used. In the case of film boiling, the temperature of the heat transfer surface rises significantly, and the heat transfer test piece may be damaged. In particular, heat transfer test equipment
Since it is assumed that the temperature of the test specimen is greatly increased, the risk of this trouble is potentially particularly high in the conventional method.

[0004]

For example, as for heat input to the plasma facing surface of the nuclear fusion device, a large heat flux instantaneously enters during plasma disruption. For example, a heat flux of 10 MW / sq.m. Occurs only between 0.1 ms and 100 ms. For instantaneous heat flux, the critical heat flux that shifts to film boiling tends to be larger than steady state heat transfer, but it has not been investigated under various conditions.

When trying to grasp the heat transfer characteristics with respect to such an instantaneous heat flux, the power supply to the heating element 3 is instantaneously increased by the power control device 2 described above.
However, in this type of heat transfer test, a large amount of power is required in a pulsed manner, so that the power available for the test is limited in places where the power that can be received from the commercial power system is limited. High-power testing is not possible, and for example, a test with a reduced heat transfer test model must be performed.This is a test that is far from verification and confirmation under actual machine conditions, and has high accuracy. You will not be able to test. Also, it is difficult to accurately execute a test with a short pulse waveform of 20 ms or less from a commercial frequency waveform.

On the other hand, there is a conventional test apparatus for supplying electric power to a heat transfer test body by controlling electric energy from a storage battery with a transistor. This is because a large amount of energy is built in the storage battery and a point where a voltage is constantly applied tends to cause trouble. Trouble is a danger such as excessive energy being supplied to the specimen and damaging the specimen, or electric shock. In particular, if a test is performed in a state of being connected to a system or a high-power chemical storage battery having a large energy, a large accident is likely to occur in the event of a trouble, so that a large accident is likely to occur. For this reason, it is desirable to perform the test with as little energy as possible inflow of the energy required for the test.

An object of the present invention is to provide a pulse heat transfer test apparatus capable of safely executing a test for accurately grasping heat transfer characteristics under a pulsed heat flux.

[0008]

If the power for the pulse test is directly collected from the commercial power system, the above-described problem occurs. Therefore, it is necessary to separate the power control device that supplies power to the heating element and the power receiving equipment from commercial power. Therefore, in the present invention, the electric energy received by the power receiving equipment is temporarily stored, and the electric energy charged and stored in a long time as compared with the heat transfer test time is instantaneously supplied to the heating element in a short heat transfer test time. . As a device that stores such electric energy, a mechanical or electrical type power storage facility such as a capacitor, a flywheel or a reactor is considered. For example, considering a capacitor, the received electric energy is charged to the capacitor, and the charged electric energy is turned on and off for a preset short time by turning on and off a switch arranged between the capacitor and the heating element.
Generate heat. Thus, a pulse-like large heat flux can be generated.

Once the heating element is energized and the test is completed,
For safety of persons engaged in the test, it is desirable to wait for the next test without charging the power storage equipment. Therefore, when the energization of the heating element is completed, the electrode of the power storage equipment is grounded via a resistor. As a result, the electric energy is extinguished from the power storage equipment, and the test preparation such as the rearrangement of the test body can be safely performed during the period when the power supply test to the heating element is not performed.

[0010] Further, since electric power equal to or higher than the pre-charged electric energy is not supplied to the specimen, even if a trouble occurs, no accident such as damage to the specimen occurs.

[0011] Such charging control and grounding control are performed by turning on / off the charging equipment that generates a DC voltage for charging the power storage equipment.
This is performed by turning off and on and off a switch of a ground circuit placed in parallel with the power storage equipment.

The present invention basically has a power receiving facility, a charging circuit, a power storage facility, a ground, a power switch, and a heating element. There is a heat transfer test surface near or in common with the heat generating element, and a transient heat transfer characteristic accompanying pulsed heat generation is examined. The power receiving equipment receives electric power from a commercial system to supply electric energy to the power storage equipment. Since power is stored for a longer time than the power supply time to the heating element, the power receiving equipment is a power receiving facility that is smaller than the power supplied to the heating element. The power storage equipment stores the received electric energy until it is supplied to the heating element. Assuming that the time for storing power is tc and the time for energizing the heating element is td, the average receiving power can be reduced to about td / tc compared to the power supplied to the heating element.

An energizing switch is provided between the power storage facility and the heating element. This switch is turned off during power storage, and does not energize the heating element. Also, the storage is completed,
When the other equipment related to the experiment such as a measuring instrument is ready, it is turned on and the heating element is energized. When the test time is over, the power is turned off and the energization is stopped. Thereby, heat can be generated in a pulsed manner, and a large heat flux can be generated on the heat transfer test surface. In addition, unnecessary heating is eliminated, and overheating and breakage of the heating element can be prevented. Even if the switch for energizing the heating element breaks down and cannot be turned off, the energy stored in the power storage equipment is not input to the heating element, so that the test apparatus or the test object is not seriously damaged.

When the energization of the heating element is completed, the power storage equipment is grounded and discharged. In addition, since the switch at the input of the charging equipment is also turned off, all parts from the charging equipment to the heating element are electrically turned off, ensuring safety during work such as replacing test specimens. You.

[0015]

FIG. 1 shows the configuration of a pulse heat transfer test apparatus according to a preferred embodiment of the present invention. The power receiving facility 1 includes a transformer, a breaker, and the like as in the related art. The power storage facility 10 is a capacitor bank that is an aggregate of capacitors that are excellent in charging and discharging in a short time. The received power is stored in the power storage facility 10, and there is a charging circuit 9 for that. The charging circuit 9 is turned on some time before the start of the experiment, and starts charging the capacitor. When the charging circuit 9 is off, all parts between the charging circuit 9 and the heating element 3 are electrically off. Power supply equipment 1
8.

When the charging circuit 9 is turned on and charging proceeds and the voltage of the power storage equipment 10 rises, the voltage is detected, and when the voltage reaches a preset voltage, the charging circuit 9 is turned off and stored at a predetermined voltage. The equipment 10 is charged. As described above, the electric power is charged into the power storage facility 10 over a long period of time, so that the electric power received is relatively small. Therefore, the power receiving equipment 1 is smaller than the conventional method. The load on the power system is also small. On the other hand, the power stored in the power storage facility 10 is supplied to the heating element 3 when a switch provided in the power control device 2 is turned on. As a result, power is consumed in the heating element 3 in a shorter time than the charging time. For example, when it is assumed that electric power from the heating element 3 of about 1 MW is supplied for 0.1 second, the net electric energy is 100 kJ. The energy to be charged in the power storage facility 10 is higher electric energy. For example, even if it is assumed to be charged at 500 kJ, it can be charged within 2 minutes by a charger of about 5 kW. A ground circuit is also arranged in the power storage equipment 10 in parallel. During charging and other than during energization, the capacitor bank of the power storage facility 10 is grounded. Even if all of the charged energy is input to the heating element 3, this means that 1 MW is supplied for 0.5 seconds, and no major trouble occurs.

The power control device 2 is a simple switch in consideration of the simplest configuration, but is a circuit using a semiconductor element and a reactor capable of high-speed switching in consideration of controlling a current waveform. The power to the heating element 3 can be adjusted by switching a semiconductor element such as a transistor by pulse width modulation, for example.

FIG. 3 shows a circuit example of the charging circuit 9, the power storage equipment 10, and the power control circuit 2. Further, a structural example of the heat transfer test body 8 is also shown. The charging circuit 9 receives commercial AC power from the power receiving facility 1 and rectifies it, and passes a current through the power storage facility (capacitor bank) 10 through a charging resistor. A switch 11 is provided at the input of the charging circuit 9, and is turned off when charging is not required. By turning off this part, the part (power storage equipment 10, power control circuit 2, heating element 3) electrically downstream from charging circuit 9 can be turned off electrically. The switch 11 can be turned on / off in the power receiving equipment, for example, in a form that also serves as a breaker of the input part of the power receiving equipment, without being the input part of the charging circuit 9.

As a capacitor bank of power storage equipment 10, for example, 400 capacitors of 15 mF
When charged to 00V, energy of 480 kJ can be charged. When 100kJ is released in 0.1 seconds, 1M
W power can be supplied for 0.1 seconds. A discharge resistor 13 and a discharge switch 12 are provided as a discharge circuit for discharging unnecessary charges in parallel with the electrodes of the capacitor. When the energization of the heating element 3 is completed, the discharge switch 12 is turned on to perform ground discharge, and the voltage of the capacitor is reduced to zero.

The power control circuit 2 supplies power to the heating element 3 while controlling the power stored in the capacitor. In this circuit, the power supply to the heating element 3 can be controlled by controlling the on / off ratio of the transistor 14. Also, a reactor 15 is arranged in the circuit to smooth the energizing current.

The heating element 3 has a tubular shape, but the surface in contact with water is the heat transfer surface 4. The tubular portion having the heat transfer surface 4 is a heating element, which is directly energized to generate heat. A conductor 16 which is a circuit for returning current is arranged in the tubular heating element 3. An insulator such as ceramic is arranged on the outside of the conductor 16 for insulation and to reduce inward heat transfer. In this cross-sectional view, the arrows indicate that the direction of the current is opposite between the conductor and the tubular heating element.

FIG. 4 shows the sequence of the experiment.
The experiment period is from time 0 second to 0.1 second in the figure, during which an electric current is applied to the heating element 3. Before this energization, for example, 1-3
Minutes before, the capacitor starts to be charged, and reaches a preset voltage at 0 seconds. After the power is supplied, the capacitor is forcibly grounded and discharged. Therefore, when no experiment is performed, the capacitor has no charge and no voltage is applied, so that the safety is high. The measurement system also operates in synchronization with the operation of the power supply. Analog data, for example, temperature data by a thermocouple, starts collecting data before the energization of the heating element 3 starts and stops after the energization ends. A timing pulse for operating a measuring instrument or the like in synchronism with the operation of the power supply also exists before and after energization as shown in the figure.

FIG. 5 shows a configuration of a test system using the pulse heat transfer test apparatus of the present invention. There is a power supply control panel 51 for managing the operations of charging, energizing, and discharging the power supply.
From the power supply control panel 51, setting of charging voltage, setting of various timings, setting of current, and the like are performed. Power control panel 5
1 outputs a timing signal to control the operation of a measuring instrument and the like. A computer that summarizes the above and sets up a data collection condition and a power supply operation condition is set by a computer that mediates with the tester.
With this system, the test apparatus operates stably and according to the tester's wishes.

[0024]

According to the present invention, since the electric power is stored and the test is performed using the stored electric power, the test on the pulse-like heat transfer characteristic can be performed without applying a large load to the system. In addition, except for the time immediately before and immediately after energization of the heating element, no voltage is applied to the equipment other than the power receiving equipment of the test equipment, and the electrical energy used for the test is limited to the stored energy. Can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a pulse heat transfer test apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional heat transfer test apparatus.

FIG. 3 is a schematic diagram of a charging circuit 9, a power storage facility 10, and a power control device 2 of FIG.

FIG. 4 is a diagram showing an operation time sequence in the pulse heat transfer test device of FIG.

FIG. 5 is a configuration diagram of a test system using the pulse heat transfer test device of FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power receiving equipment, 2 ... Power control device, 3 ... Heating element, 4 ... Heat transfer surface, 5 ... Coolant, 6 ... Water stopcock, 7 ... Test container, 8 ... Heat transfer test object, 9 ... Charging circuit, DESCRIPTION OF SYMBOLS 10 ... Electric storage equipment, 11 ... Switch, 12 ... Discharge switch, 13 ... Discharge resistance, 14 ... Transistor, 15 ... Reactor, 16 ... Conductor, 17 ... Insulator, 18 ... Power supply equipment.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuhiro Masuhara 3-1-1, Sakaimachi, Hitachi-shi, Ibaraki F-term in Hitachi, Ltd. Hitachi Plant 2G040 AB08 BA24 CA02 CB03 EA02 EA11 EA13 EB02 EC02

Claims (4)

[Claims] A power storage device for storing electric energy as a power supply capable of generating heat in a pulse form, a heating element connected to the power storage device due to Joule loss due to an electric resistance, and a switch capable of turning on and off between the two. A pulse heat transfer test device, which is arranged. 2. A pulse heat transfer test according to claim 1, wherein a capacitor bank is used as said power storage equipment, and charging of said capacitor bank, energization of a heating element, and grounding of electrodes of said capacitor bank are repeated. apparatus. 3. The pulse heat transfer test apparatus according to claim 1, wherein the material constituting the heat transfer surface is directly energized to generate heat. 4. The pulse heat transfer test according to claim 1, wherein the heating element retaliates the current with an assembly of a tubular outer wall and an inner conductor rod or a thin wire to generate heat on the outer wall or the inner conductor. apparatus.